This application is a continuation-in-part of International Application No. PCT/BR99/00035 having a priority date of Jun. 19, 1998.
1. Field of the Invention
The present invention relates to a continuous process for manufacturing decorative panels and similar products used in decoration and visual communication. This process provide panels of very high quality, to fulfill the market segment that demands more sophisticated and aesthetically pleasing products.
2. Description of the Related Art
Manufacturing methods to obtain decorative reinforced plastic laminates are known from Canadian Patent No. 1,011,240 on behalf of Pidgeon, U.S. Pat. No. 4,126,719 on behalf of Koyanagi et al., and PCT Publication PI 9403679-9 on behalf of Fusco.
PCT Publication PI 9403679-9 discloses a continuous process for manufacturing decorative panels wherein a pair of fiber reinforced resin layers are formed on opposite sides of a decorated sheet and thermally cured in a single step.
A disadvantage of the foregoing process is that it involves thermal curing of unsaturated resins. It has been found that thermal curing of unsaturated resins is harmful to the final product quality because of shrinkage. The amount of shrinkage varies with the kind of resin, the curing temperature, the fillers added to the resin, and the kind of manufacturing process used, among other factors. In the case of continuous laminating for manufacturing products used for decoration and visual communication, the choice of the resin leaves very few alternatives.
In PCT Publication PI 9403679-9, the components of the continuous composite panel, that is, the two carrier/molding films, the two resin layers, the two reinforcement layers, and the decorated sheet, each have a different elongation coefficient. The difference in elongation coefficients can cause deformations, adversely affecting the quality of the final product. This is due to a combination of factors, such as stretching of the components when tensed during their transport through the long steps of the process, the frictional resistance of the laminate to sliding on the platform, the length of the platform, and the necessity to submit the composite panel to pultrusion.
Also, the presence of peroxide catalysts in the resin generates porosity in the laminate, and, moreover, doesn""t allow the production line to be stopped for fittings, controls, material refill, production shifts, thereby making the operation very complex.
Another obstacle to obtaining a high quality product by an economically viable process using heating for curing the laminate, is the restriction in the choice of the decoration materials, both the substratum and the inks.
A further problem is the entrapping of air into the compound. It has been discovered that reinforced plastic laminates formed by the method disclosed in PCT Publication PI 9403679-9 often contain undesirable air bubbles, that are entrapped during process, especially when high production speed is pursued. Such air bubbles, even if of small dimensions, expand when exposed to the sun, damaging the appearance of the panel, harming the transparency, and causing delaminating between the layers.
The entrapping of air bubbles can dramatically worsen depending upon the way the decorated sheet and any upper molding film are introduced in the production line.
In PCT Publication PI 9403679-9 (FIG. 1) both the decorated sheet and a molding film are pulled from reels, sliding underneath respective guide axes or rollers, which are spaced apart from the composite so as to avoid contact with the sticky resin. The decorated sheet and molding film are laid by gravity, thereby entrapping air bubbles and forming barriers that hinder removal of the air bubbles by the laminating cylinders near the end of the production line.
A high quality, structural, reinforced plastic laminate, demands a high reinforcement content, to satisfy sophisticated applications requiring large seamless panels such as backlight facades in high buildings, elevated gas station signs or other applications where handling and installation of large panels is difficult, due at least in part to the panel""s own weight.
Moreover, in a thermal curing process, the laminate can not reach its full cure in the production line, since it would demand impossible dimensions. To complete the curing at room temperature takes several days, keeping the laminate perfectly flat, otherwise any deformation becomes permanent.
There remains a need for high quality, structural panels for use in decoration and visual communication.
In view of all the limitations above mentioned, and to solve them, a new continuous manufacturing process was developed, comprising a series of interactive innovations that will be properly detailed in the description of the process, providing, as a final result, the following advantages:
I. In the process:
easier operation because of the UV curing features and the elimination of the catalyst, allowing the operation to be switched on and off, again an again;
higher operation speed (up to 30 meters per minute against approximately 5 meters per minute in the thermal curing process), dramatically increasing the productivity; and
shorter curing area (from 30 meters to 1 m approximately).
II. In the product:
perfect flatness, essential for visual communication and decoration panels;
dimensional stability because of the full curing on the production line;
homogeneity of the material due to elimination of the decorated sheet substratum by dispersion or removal;
porosity free, because the peroxide catalyst elimination;
high resistance/weight ratio due to the reinforcement content;
air bubble free;
economy in the product final cost (reference 30%, according to preliminary tests accomplished with production speed of 25 m/min); and
long lasting performance.
A first aspect of the present invention is generally characterized in a continuous process for manufacturing decorative panels including the steps of forming a first continuous fiber reinforced resin layer, laying a continuous decorated sheet on the first fiber reinforced resin layer, forming a second continuous fiber reinforced resin layer on the continuous decorated sheet, eliminating a substratum of the decorated sheet so that the first and second fiber reinforced resin layers can join one another to form a continuous consolidated strip of fiber reinforced resin with an image suspended therein, curing the continuous consolidated strip, and cutting a panel from the continuous consolidated strip. The step of eliminating the substratum of the decorated sheet can be performed by alternately flexing the laminate to fragment or disintegrate the substratum, for example using a corrugated profiling mechanism, by dissolving the substratum, or by simply removing the substratum once the image printed thereon has transferred to the first fiber reinforced resin layer.
Another aspect of the present invention is generally characterized in a continuous process for manufacturing decorative panels including the steps of forming a first continuous fiber reinforced resin layer, laying a continuous decorated sheet on the first fiber reinforced resin layer, at least partially curing the first fiber reinforced resin layer with the decorated sheet thereon, forming a second continuous fiber reinforced resin layer on the continuous decorated sheet to create a continuous strip of panels, curing the second fiber reinforced resin layer, and cutting a panel from the continuous strip of panels. The first curing step can be performed using a thermal curing unit, a UV light source, or any other suitable type of curing unit. The final curing step is preferably performed using a UV light source but can be performed using any of the other curing units noted above.
Yet another aspect of the present invention is generally characterized in a continuous process for manufacturing decorative panels including the steps of forming a first continuous fiber reinforced resin layer, laying a continuous decorated sheet on the first fiber reinforced resin layer, laminating the first fiber reinforced resin layer and the decorated sheet to form a first laminate, forming a second continuous fiber reinforced resin layer on the first laminate, laminating the second fiber reinforced resin layer together with the first laminate to form a second laminate, curing the second laminate, and cutting a panel from the second laminate. Preferably, one or both of the laminating steps are performed by passing the panel components through sets of laminating cylinders. The decorated sheet is preferably fed directly into a set of laminating cylinders in the first laminating step to minimize entrapment of air bubbles in the composite.
Still another aspect of the present invention is generally characterized in a decorative panel comprising a decorated sheet disposed between first and second fiber reinforced resin layers, the decorated sheet including an image printed on a substratum that has been eliminated, the first and second fiber reinforced resin layers joining each other to form a consolidated structure without distinct layers. In a preferred embodiment, the substratum is in a fragmented or disintegrated condition and the fiber reinforced resin layers join each other through the substratum.
Yet another aspect of the continuous process proposed by this invention consists of forming two fiber-reinforced resin layers, catalyst free, one layer on each face of a continuous decorated sheet, so that such sheet is wet by the resin of the two layers, front and back, and that such two fiber-reinforced resin layers join each other through the sheet, becoming an only material. Such a continuous compound strip, set between two carrier/moulding films, is forced to pass, in sequence, through laminating cylinders and lamination/pultrusion mechanisms, through at least one UV radiation photocuring set, and finally, through cut and finishing set of the panels.
The panels so obtained consist in a laminate/pultruded constituted by two fibers-reinforced resin layer, formed one on each face of a decorated sheet, and the two fiber-reinforced resin layers are adequately consolidated and join each other through the decorated sheet, becoming an only material that produces decorative panels having a smooth, glass-like surface, free of deformations and porosity.
Layers of superficial finish can optionally be provided by the incorporation of a front and/or back film, by incorporation of a layer of gel-coat or by incorporation of a veil of polyester or the like.
The above and other features and advantages of the present invention will be further understood from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings.